This invention relates generally to more vibration resistant support means for a double ended tungsten-halogen lamp and more particularly to an improved mount structure for such type lamp in various reflector lamps.
Reflector lamp units of various types which employ a double ended tungsten-halogen lamp as the light source enjoy wide spread commercial use in many applications including vehicle and general service lighting applications. In one such type lamp unit, a parabolic aluminized reflector (PAR) member is employed which cooperates with the light source of the lamp unit to project illumination forwardly in an efficient manner. In a different reflector lamp unit of the sealed beam type now used widely in automotive vehicles, aircraft and boats, the aforementioned light source is similarly positioned substantially at the focal point of the reflector member with the lamp unit further including a lens or cover member being secured to the reflector. Such latter type lamp unit generally has the light source aligned substantially along the main or longitudinal lamp unit axis with the further axially aligned tungsten filament in the light source being similarly positioned along the axis.
Various type tungsten-halogen lamps can also be employed as the light source in the aforementioned reflector lamp unit constructions. For example, the lamp construction can employ a vitreous lamp envelope formed with fused quartz but which generally further requires that the lead wires supporting the lamp filament be hermetically sealed within the lamp envelope with thin refractory metal foil elements. Alternately, various glass-halogen lamp constructions can be employed wherein the vitreous lamp envelope is formed with a refractory glass, such as an aluminosilicate glass composition, and which differs structurally from a quartz-halogen lamp primarily with respect to the means employed to hermetically seal the filament lead wires to the lamp envelope. In this regard, a closer match in thermal expansion between the selected glass material and molybdenum metal, generally employed to form said filament lead wires, enables elimination of the foil elements conventionally employed for a hermetic seal in the quartz-halogen lamp construction. Both quartz-halogen and glass-halogen lamps further include a fill of rare gas, such as argon, xenon and krypton, together with a vaporizable halogen compound, such as an alkyl halide substance, also being contained within the lamp envelope. The lamp fill is generally employed at substantially superatmospheric pressure in order to improve lamp efficiency at higher operating temperatures.
A typical sealed beam headlamp construction utilizing a tungsten-halogen lamp for its light source is still further disclosed in U.S. Pat. No. 4,810,932, which is assigned to the assignee of the present invention. As therein disclosed, the double ended lamp is physically supported within the reflector member with support means being physically attached to relatively thin filament lead wires. Connection of the external supporting leads to relatively stiff post members sealed at the rear base portion of the reflector member makes the mounted lamp prone to mechanical failure of the support means based on a number of considerations. Having the support leads less rigid than the post terminals produces a vibrational resonant frequency for the overall mount construction which now resides in a range commonly encountered during vehicle operation. Moreover, flexure of such mount construction under vibration and mechanical shock becomes concentrated at the still smaller cross section filament lead wires being employed. Since the smaller size filament lead wires are commonly joined to the supporting lead with significant heating, such as welding or brazing, there can also be significant metallurgical degradation produced at or near to these points of greatest flexure. It can be expected under these circumstances that such prior art lamp becomes thereby prone to mechanical failure from eventual fatigue or rupture of the protruding filament lead wires over a period of time dependent upon such additional factors as mass of the suspended inner lamp, thermal history of the filament lead construction and severity of the external vibration forces being encountered by the lamp unit.
While not depicted in the above described prior art sealed beam headlamp unit, it is also common practice to include metalic heat and/or light shield elements in the lamp construction. These elements are usually crimped along the inner lamp envelope during manufacture and often become disengaged thereafter due to mechanical vibrations being experienced with the lamp unit during use. A still different light shield means currently in commercial use employs a black color coating which is deposited over a portion of the inner lamp envelope. Precisely located this coating has proven difficult to achieve during lamp manufacture and any mislocation of the coating detrimentally effects the lamp performance. An additional problem now encountered by the lamp manufacturer with such coating is satisfactory outgassing of the coating material since both appearance and performance defects can occur in the assembled lamp unit if not properly carried out.
Accordingly, one object of the present invention is to increase the vibration resistance of a mount construction for a double ended tungsten-halogen lamp.
Another object of the invention is to provide a more vibration resistant mount construction for a double ended tungsten-halogen lamp which enables both physical support and electrical connection of the suspended lamp to be made in a simpler manner.
Further still, it is an object of the present invention to provide means to improve the sealing of the members of the tungsten-halogen lamp.
A still further object of the present invention is to provide a mount structure for a double ended tungsten-halogen lamp which employs novel vibration damping elements as the means whereby physical support, electrical connection and light shielding of the lamp is achieved.
Still another object of the invention is to provide more vibration resistant reflector lamp units employing a double ended tungsten-halogen lamp as the light source.
These and still further objects of the present invention will become apparent upon considering the following detailed description for the present invention.